Lettuce disease draws close study

A potentially new disease of lettuce detected in the Salinas Valley last spring is no cause for alarm at this time, according to UC Cooperative Extension researchers.

"The lettuce crown rot disease is of very limited distribution and found in only a few fields," said Steve Koike, plant pathology farm advisor for UCCE in Monterey County. "Only a very small portion of the Romaine lettuce crop in California is affected by the development. Currently, there is no change in the quality and availability of California Romaine lettuce, nor is any anticipated for next season."

Koike is studying the cause of the disease, characterized early on by yellowing and stunting, and later by plant wilting and collapse. A small black sunken area is found on the crown and upper tap root of affected plants.

The Koike lab has isolated a gray-green, sterile fungus from all samples found at all locations. "While the consistent recovery of this fungus makes it likely it is involved with the problem, documentation is needed before we reach such a conclusion," Koike said.